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Remington 6.8 SPC Guide.

INTRO:
I've been shooting the Remington 6.8 SPC for approximately 4 years now. I've had 7 different uppers from which I have tested pretty much every bullet/powder combination available. I have put this thread together to help and better inform current users and potential buyers understand what the 6.8 SPC is and what it isn't.

WEAKNESSES:
1. Not a long range cartridge. This is mainly due to the lack of high BC bullets.
2. Still no affordable Plinking Ammo available. Not a cartridge that I would take to a high round count class, unless you can use handloads.

BARREL LENGTHS:
The most popular barrel length is the 16" barrel. The 6.8 SPC is a very efficient cartridge as it uses the medium fast powders from H4198 to H335. When going from a 16"-20" barrel, you will generally see 75-125 FPS increase. Since the 6.8 SPC is such an efficient cartridge, the 18" barrel is the longest I would recommend. Here are the best Barrel Length/Gas Port Locations:

14.5"-below: Carbine Length Gas System.16": Mid-Length preferred. Carbine Length Gas System, if properly gassed is OK.18": Mid-Length pretty much a must.20": Mid-Length and Intermediate Length preferred. Rifle Length will work with the slower powders, but may short stroke with the ever-growing light powders/fast powder combinations.

TWIST RATE:
Twist Rate has very little effect on pressure when compared to the Chamber and the Land to Groove Ratio.

CHAMBERS:
The 6.8 SPC was designed as a Combat Cartridge. One of the most important things about the AR is reliability, especially if you plan to use the 6.8 SPC for serious work. The SPCII and 6.8x43 Chambers are reliable and very accurate. The SPCII and 6.8x43 Chambers have a longer throat which allows you to shoot the hotter loads without worrying too much about pressure signs. For anyone that has a SAAMI Chamber, the one thing you could do is have someone lengthen the throat to the Improved Chamber specs.

BARREL GROOVES:
This, along with the proper chamber, is one of the most important ways of reducing the pressure. The best are the 5R, 3-Groove, and Polygonal barrels followed by the 4-Groove. The 6-Groove is OK.

COMMON SPECS:1:10"/6-Groove/SAAMI Chamber:
The original specs.1:10"/6-Groove/SPCII Chamber:
This combination allows for approximately 75 FPS over the 1:10"/6-Groove/SAAMI Chambered Barrels.1:11"/4-Groove/SPCII Chamber:
This combination allows for approximately 25 FPS over the 1:10"/6-Groove/SPCII Chambered Barrels.1:12"/3-Groove/6.8x43 Chamber or 1:11.25"/5R/6.8x43 Chamber:
This combination allows for approximately 25 FPS over the 1:11"/4-Groove/SPCII Chambered Barrels.

MAGAZINES:
The 6.8 SPC uses its own dedicated magazines. You can load 5-8 6.8 SPC rounds in a 556 magazine, but after that, the magazine will begin to bulge. The three main 6.8 SPC magazine manufacturers are Barrett, C-Products, and PRI. All three are different in price and allow for different COAL.

Barrett Magazines:
$40-$50. Available in 30 round magazines only. They are approximately 1" longer than standard USGI 556 Magazines. The max you can load your ammo in the Barrett magazines is approximately 2.260", which is shorter than the C-Products and PRI. Best used in Tactical applications due to the length of the magazines.

C-Products:
$12-$15. Available in 5, 10, 17, and 25 round magazines. The 5, 10, and 17 rounders have straight bodies, while the 25 round magazines are curved. These are very reliable and affordable except for the 17 round mags, which are very problematic. The C-Products CS Springs can be a little weak, so it is recommended that they are replaced with the ISMI or Superior Shooting 556 30 round magazine springs for the best reliability. The max you can load your ammo in the C-Products magazines is approximately 2.285". With the ISMI or Superior Shooting Magazine Springs, they are the best bang for the buck of the 3.

PRI (Precision Reflex, inc):
$30-$40. Available in 5, 10, 15, and 25 round curved magazines. The 25 round magazines are similar in length to the 556 30 round magazines. The max you can load your ammo in the PRI magazines is approximately 2.305". The PRI magazines are very popular with the 6.8 SPC Precision shooters who like to load their rounds longer, for increased precision.

MUZZLE THREADS:
The most common muzzle thread for the 6.8 SPC is the 5/8x24, so any .308 muzzle device with the 5/8x24 threads can be used. Stag uses the 1/2x36 muzzle threads, which is the 9mm muzzle thread.

Reloading for the 6.8 SPC

INTRO:
I put this thread together to help out with reloading for the 6.8 SPC. Hopefully this will answer some of the most common asked questions.
Note: Even though this will be geared for the 6.8 SPC, most of this info can also be used for other calibers.

BRASS:
There are three manufacturers of 6.8 SPC Brass. SSA, Hornady, and Remington. SSA and Hornady use the Small Rifle Primers Pockets, while Remington uses the Large Rifle Primers Pockets.
NOTE: SSA has recently made batches of SSA Brass with Large Rifle Primer Pockets.

SSA:
The SSA brass generally lasts 10-15 reloads and holds the most powder.

Hornady:
The Hornady brass is very similar to the SSA brass, but generally holds 1 less GR.

Remington:
The Remington bras is generally a little softer than the SSA brass, so they don't last as long, but you should still be able to get at least 5-8 reloads.

PRIMERS:
There are 4 basic types of primers: Regular, Magnum, Benchrest, and Military.

Standard Primers:
These are the standard primers. Generally, they are great for plinking. They will produce decent velocities and good accuracy. When the primer pockets start to loosen up, the standard primers are real loose and may pop out, especially when you have a hot load.

Magnum Primers:
Magnum primers will produce more velocity, but they also produce more pressure and a higher SD. They are good for bulky powders. Generally, magnum primers can produce as much as 40 FPS more over the Standard Primers, which is equivalent to 1/2 GR powder.

Benchrest Primers:
Known for their consistency. Great for accuracy, but they are generally more expensive.

Military Primers (CCI #41 and CCI #34):
Similar to the Magnum primers in that they are Magnum Primers, but they have thicker cups and they are a little thicker, which is great for when the primer pockets start loosening up.

RELOADING DIES:
There are several different dies available from Hornady, RCBS, Lyman, and Redding.

Re-Sizing Dies:
One of the biggest questions going around is whether to get the Regular Full-length Sizing Dies or the Small Base Sizing Dies. For auto loaders, such as the AR-15, the Small base dies were designed for reliability in auto loaders. Although many people have used the regular full-length sizing dies for years with no issues, the small base dies are just an extra security.

Seating Dies:
The RCBS dies and the Hornady Seating dies are both very affordable dies that work very well. The Hornady has a sleeve that assists with aligning the bullet. With the Hornady Seating Die, you can also later get the Micro Seating Adapter, which makes it easy to adjust.

Crimp Dies:
Although, crimping the bullets is not necessary, it is highly recommended to crimp the bullets, to prevent bullet set-back. A very affordable crimp die for the 6.8 SPC is the LEE FCD. It is easy to set up and works with or without cannelures on the bullets. In testing that I conducted, the LEE FCD produced a slight (10 FPS) increase and a slight increase in accuracy.

CANNELURE TOOL:
Another highly recommended tool is a Cannelure Tool. Although you can crimp a non-cannelured bullet using the Lee FCD, placing a light cannelure on the bullet will give it the extra grip for the Lee FCD, without sacrificing too much accuracy. If the bullets don't come with cannelures, you can roll your own.
An example of a cannelure tool is the Corbin Cannelure Tool.

HEADSPACE GAUGE TOOLS:
For anyone that reloads, the Hornady Headspace Gauge Kit and the Wilson Case Gauge are two highly recommended tools. They both do the same thing, but they are slightly different. These tools measure the amount that the shoulder is bumped back, which is very important because if the shoulder is not bumped back far enough when re-sizing, you will get brass stuck in your chamber. If the shoulder is bumped back too far, you will have excess headspace and your brass life will decrease.

Wilson Case Gauge:
Very basic tool that allows you to check to see if the brass was re-sized properly. The Wilson Case Gauge is caliber specific, so you have to get one for each caliber.

Hornady Headspace Gauge Kit:
The Hornady Headspace Gauge Kit is a little more complicated to use, but with the supplied bushings, you can use it with pretty much any caliber. (The 6.8 SPC uses the "B" Bushing.).

How to use the Hornady Headspace Gauge:
As already mentioned before, the Hornady Headspace Gauge measure how much you have bumped the shoulder back when you re-size your brass. Along with the tool, you will also need a set of calibers. The tool actually attaches to the calibers. Here are the steps:

1. Measure several fired pieces of FIRED brass and record the readings, but use the lowest reading. Generally, the reading is going to be around 3.355"-3.360". (The factory brass is generally 3.350").
2. Lube your brass, re-size your brass, and measure it using the Hornady Headspace Gauge. Ideally, you want to bump the shoulder back .004". Let's say your fired brass is generally 3.355". When you re-size them, you want to bump the shoulder back to at least 3.351".

If you have more than one 6.8 SPC AR, unless you want to keep the brass separate, which is a pain in the ass and not worth it, I would measure a couple of pieces of fired brass from each barrel and take the lowest reading and bump the shoulder back .004" to ensure reliability in all of the barrels.

NOTE: For other calibers, such as the 5.56, I like to bump the shoulder back to the original brass specs to ensure that the ammo feeds reliably in all ARs. I've been to the range with my 5.56 and I tried shooting my ammo in another AR and it had issues because the ammo was set up for my AR. Now, I just re-size the brass back to the factory brass specs. Just something to consider.

Bullets for the 6.8 SPC.

INTRO:
I have put together this thread as an informative thread for the new guys or anyone else who needs help with selecting the correct .277 bullets for reloading for the Remington 6.8 SPC.

Before I begin, I just want to touch up on the Remington 6.8 SPC. If you are using the 6.8 SPC in an AR-15, there is an OAL that you have to keep in mind. With the Barrett magazines, I would not load the ammo longer than 2.250". With the C-Products, I would not load the ammo longer than 2.280". If you have PRI magazines, I would not load the ammo longer than 2.295". Also, due to the limited powder capacity, it is best to load bullets in the range of 90-135 Gr.

POWDERS:
After doing a lot of testing, I have separated the bullets into the following categories: 90 Gr. bullets, 100-115 Gr. bullets, 120-135 Gr. bullets, 90-115 Gr. bullets, and 90-135 Gr. bullets.

Best Powders for 90 Gr. Bullets:
If you plan on just using the 90 Gr. bullets, I would use the following powders:
1. Reloaders 7. (Extruded)
2. H4198. (Extruded)
3. X-Terminator. (Ball)
4. AA2200. (Ball)

NOTE: You may see the letter "BT" (Boat-Tail) in front or after the above ammo types. BT stands for "Boat Tail" and refers to the base of the bullet. A "Boat Tail" is a sloping end which narrows gently at the base of the bullet, so that the cross-section resembles the shape of a boat's hull. The boat tail shape reduces drag on a bullet, helping it to retain velocity and resist deflection from crosswinds, but causes the bullet to take longer to "settle" after leaving the barrel compared to a standard "flat-base" bullet. Boat tail bullets are usually selected for long-range shooting, while the flat-base bullet shape tends to be more accurate at short ranges. A "HPBT" bullet is a "Hollow Point Boat Tail" bullet.

The last thing I would like to explain is a Cannelure. A Cannelure is a cut or pressed groove (or grooves) around the shank of a bullet. Cannelures provide an area into which the case mouth may be securely crimped. Military ammo has cannelures to prevent bullet set-back. Bullets with cannelures are not generally used in match ammo because cannelures may decrease the accuracy of the bullet. For Military/LE purposes, bullets with cannelures are preferred. For sniper type applications, bullets without cannelures are usually used.

HOME PROTECTION/SHTF:
Penetration and Fragmentation are key for Home Protection/LE applications. 10-12" is ideal to ensure that it will reach the vital organs.

B. Negatives:1. Expensive. ($30-40).2. Issues with the followers being too short (Not actually PRI's fault as the followers are made by Magpul.).3. Fit very tight in the magazine well.

CONCLUSION:For most uses, the C-Products 25 Round Magazines are the best bang for the buck. The only negative about the C-Products Magazines is the springs are a little weak. I highly recommend replacing them with the ISMI or Superior Shooting 556 30 round magazine springs, which will last forever. For Precision Shooting, the PRI Magazines are a better choice because they allow a COAL of 2.305".